1. Field of the Invention
The present invention relates to an electrode. More particularly, it relates to an electrode structure wherein an electrochemically active sheet is fixed so as easily to be attached or removed, on a foraminous planar electrode support which is fixed on a body of a large electrolytic cell by welding etc.
2. Description of the Prior Art
Anodes and cathodes are fixed by welding on a body of a large heavy electrolytic cell such as PPG-Glanol electrolytic cell known as a typical bipolar electrolytic cell for electrolyzing an aqueous solution of an alkali metal chloride to obtain an alkali metal hydroxide by using an asbestos diaphragm as a typical diaphragm process. Therefore, in order to form an electrochemically active material on the electrodes or to remove a deactivated material from the electrodes, it has been necessary to move the body of the cell in the treatment and various disadvantages have been found in the operations.
It has been proposed to reduce hydrogen overvoltage by forming an electrochemically active layer on a surface by leaching out a part of components of an alloy for a cathode with an alkaline material. However, a cathode treated by the conventional process causes disadvantages such that conditions for generating hydrogen gas such as sizes of generated hydrogen gas and residence of hydrogen gas on the surface of the cathode are not satisfactory. The reduction of hydrogen overvoltage has not been satisfactorily affected to an expected reduction of a cell voltage.
In order to improve these disadvantages, an improved individual deposition of asbestos and a control of an amount of deposition of asbestos have been studied. However, concentrations and purities of the resulting chlorine gas and an alkali metal hydroxide are highly affected by the conditions. A desired result is not expected in view of such conditions. The activated effect does not continue for a long time by one treatment for leaching out a part of the alloy. It is necessary sometimes to retreat the electrodes. Only the surface portion of the electrodes is etched by one treatment, however, the etched portions of the electrodes are increased by the repeat treatments whereby desired electrolytic characteristics and strength of the electrodes may be lost.